Just a disclaimer - I'm new to using Mp3Gain and trying to learn more, so please bear with me if I'm misunderstanding the technical aspects of it...

My Mp3 collection is mostly Rock and Metal with some Classical and Electronica mixed in, so there are some major discrepancies in song volume between the genres. I read some stuff on Mp3Gain and it sounded like the least intrusive and overall best way of normalizing the volume. I then ran track analysis (and later album analysis) on all of the songs and I figured that 92db would be a pretty good level to compromise. So when I applied that level of gain to the collection (using Track Gain) and began listening, a lot of songs sound like they're ran through a compressor. In other words, let's say that the song starts out with an electric guitar riff, no other instruments playing and the volume level sounds like it's at 92db, when the rest of the band kicks in, it sounds as if it "sucks" the volume down to a lower level, similar to how a compressor behaves. If in the song, it goes to a single instrument again, then it seems to get louder and then sucks it back down when the band kicks in again.

Now I'm sure there's a better technical description of what's going on here, perhaps it's applying gain to the "valleys" in the volume to make it more equal throughout the song (although that's definitely NOT what I want), but I'm kind of in the dark on this and haven't been able to Google anything to help me find an answer. I just want to know what I'm doing wrong when applying the gain.

Another caveat to this, when I undid all of the gain changes in Mp3Gain and looked at the tag data, I saw that the APE and ID3v2 tags still had the Track and Album gain values in there. I also noticed that after undoing the gain, they still sound like they're compressed. Do I need to completely delete all of the ReplayGain and Mp3Gain values out of the tags and then delete the tag itself for it to return to normal?

Thanks in advance for any help that you're willing to throw my way and explain to this newbie what's going on.

Properly coded ReplayGain aware players will apply a constant gain to files which contain RG information. Since it's constant, the dynamics of the song are preserved, unless you run into clipping issues (and even that can be avoided by some players). So any "pumping" you hear is likely due to hardware problems (speakers, amp, etc.), or some normalization DSP/misconfiguration in whatever player you use.

Please provide a step by step breakdown about what is happening, this whole thread is very confusing, since you talk about a lot of different playback softwares, and it's not very clear to me how they are configured and what kind of files you tried to play back and so on.